fix race

Makefile

@@ -25,6 +25,11 @@ build:
 test:
 	go test ./...
 
+# Run tests with race condition detection
+.PHONY: test-race
+test-race:
+	go test -race ./...
+
 # Build for all supported architectures
 .PHONY: buildall
 buildall: clean
@@ -78,6 +83,7 @@ help:
 	@echo "  build      - Build for current architecture"
 	@echo "  buildall   - Build for all supported architectures"
 	@echo "  test       - Run tests"
+	@echo "  test-race  - Run tests with race condition detection"
 	@echo "  check-style - Install golangci-lint and run code style checks"
 	@echo "  clean      - Remove build artifacts"
 	@echo "  run        - Build and run the application"

mock_smtp_server.go

@@ -165,10 +165,10 @@ func (s *MockSMTPServer) Reset() {
 }
 
 func (s *MockSMTPServer) acceptConnections() {
-	for s.running {
+	for s.isRunning() {
 		conn, err := s.listener.Accept()
 		if err != nil {
-			if s.running {
+			if s.isRunning() {
 				fmt.Printf("Accept error: %v\n", err)
 			}
 			continue
@@ -178,6 +178,12 @@ func (s *MockSMTPServer) acceptConnections() {
 	}
 }
 
+func (s *MockSMTPServer) isRunning() bool {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.running
+}
+
 func (s *MockSMTPServer) handleConnection(conn net.Conn) {
 	defer conn.Close()